Rugs and carpets in general are formed from tufted synthetic yarns threaded through a primary backing or substrate and adhered to a secondary backing by means of a laminating adhesive are widely used.
Double-backed tufted carpets are generally made by looping threads of pile fibers through an inexpensive woven or unwoven textile base, known as the primary substrate. The thread is looped through the primary substrate in one continuous length constituting a complete row of pile in the carpet. The thread is pulled tightly against the underside of the primary substrate, but the loops can remain connected or be severed, depending on whether a loop pile or a cut pile carpet is desired. The pile fibers are then anchored to the primary substrate in this arrangement by the application of a laminating adhesive. The double-backed tufted carpet is completed by applying to the wet underside of the primary substrate a further backing material known as the secondary fabric or as scrim which serves to improve the dimensional stability and appearance of the carpet. Primary backings and secondary backings are often formed from jute, burlap or melt fused fibers.
Many types of laminating adhesives have been utilized for the bonding of the primary backing to the secondary backing. One type of polymeric adhesive is based upon a carboxylated styrene-butadiene copolymer. However, these polymers exhibit a strong odor. Vinyl acetate/ethylene emulsions have been widely used as laminating adhesives to formulate carpet backings and they offer excellent flexibility, odor resistance and tolerance to inorganic fillers.
In the manufacture of carpeting, there have been developments which are directed to improving the water resistance of the carpet and particularly the spill resistance, i.e., the ability to prevent spilled liquids from permeating to the underside of the carpet. Indoor carpets, which, although not designed for contact with liquids do, on occasion, encounter liquid spills and large spills often permeate through the carpet and create significant problems. Not only can the spill damage the underlying floor, it can remain absorbed within the carpet and inaccessible by various cleaning methods. Solutions for producing spill resistant carpets have included the application of a spill resistant coating onto the carpet precoat, thereby, adding an essentially impermeable layer between the carpet and the underlying floor. Wax, silicone-based compositions, hydrophobic acrylate resins and so forth have been used in developing spill resistant carpets.
The following publications are representative of the state of the art with respect to use of polymeric compositions in producing carpets.
U.S. Pat. No. 4,239,563 (Iacoviello, 1980) discloses the use of vinyl acetate-ethylene copolymer emulsions as laminating adhesives for carpet backing. Vinyl acetate/ethylene copolymer emulsions having a Tg of from −35 to about −10° C. protected with poly(vinyl alcohol) and incorporating a small amount of maleic acid or triallyl cyanurate showed good tuft lock as compared to carboxyated styrene-butadiene latexes.
U.S. Pat. No. 4,735,986 (Iacoviello, 1988) discloses vinyl acetate/ethylene emulsions prepared using a stabilizing system based upon a mixture of polyvinyl alcohols, one being 86-90 mole percent hydrolyzed and the other being at least 98% hydrolyzed and a polyalkoxylated surfactant. These emulsions are used as a laminating adhesive for carpet backings.
WO 00/09798 (Tabor et al., 2000) discloses an aqueous dispersed polymeric composition for preparing spill resistant carpet backings. The compositions are based upon polymeric materials such as butadiene-acrylonitrile latexes, polyurethane dispersions ethylene-vinyl acetate latex, etc., an inorganic filler, and a hydrophobic acid. Methods described in U.S. Pat. No. 3,644,262 and 4,164,489 were suggested for forming ethylene-vinyl acetate latexes suited for producing spill resistant carpets. Other solutions for improving spill resistance of carpets have relied on the application of wax, silicone-based compositions, hydrophobic acrylate resins and so forth.
U.S. Pat. No. 3,644,262 (Stehle et al., 1972) discloses the emulsion polymerization of vinyl acetate and ethylene to produce a polymer suited for paint applications. Emulsion polymerization is carried out under conditions to increase ethylene concentration, e.g., the unreacted vinyl acetate content is maintained at a level below about 3% and preferably below 1% by weight.
U.S. Pat. No. 4,164,489 (Daniels et al., 1979) discloses a continuous process for producing a laminating adhesive comprised of polymerized units of vinyl acetate and ethylene.